Method of and apparatus for treating ores



Sept. 2, 1930. J. M. CALLOW METHOD OF ANDAPPARATUS FOR TREATING ORESFiled Jan. 15, 192'? 4 Sheets-Sheet 1 [[[MIIIIIIHW lNl/E/VTOR ATTOR/VEVS Sept. 2, 1930. J. M. CALLOW METHOD OF AND APPARA'TUSFORTREATING "ORES Filed Jan. 15, 192? 4 Shets-Shqet 2 J. M. C ALLOWMETHOD OF AND APPARATUS FOR TREATING ORES Sept. 2, 1930.

4 Sheets-Sheet 3 Filed Jan; 15, 1927 INVENTOR:

l1 TTOR/VE VS J. M. CALLOW METHOD OF AND APPARATUS'FOR TREATING ORESSept. 2, 1930.

Fiied Jan. 15, 1927 4 Sheets-Sheet 4 y I 3 4 m v ATTORNEYS.

Patented Sept. 2, 1930 UNITED STATES PATENT OFFICE JOHN m. CALLOW,.O FNEW YORK, N. Y., ASSIGNOB TO UNION CARBIDE SALES COMPANY, A ooRroRA'rIoNoruwEsT VIRGINIA Mari Ion or AND'APPARAT s FOR TREATING cans Applicationfiled January 15,' 1927. Serial No. 161,286

It has been found desirable'to film certain crushed ores with acetyleneduring grinding and preparatory toi'roth flotation. By film ing withacetylene is meant bringing minsevere tei' means excess absor tion ofacetylene by -the-water and, there ore, unnecessary exeral particles toacondition in which they are amenable to flotation. In easeof'copperores, for example, the so-called oxid zed ores,

including carbonates *and silicates, require,

filming. These have been flotable when thus treated with acetylene.While various ways have been suggested and tried for this treatment, themost efiicientand practical method has been found to be the treatment ofthe ore I with gas during the'process of wet grinding. 'A common form ofwet grinding mill is the conical ball mill frequently arranged in.

closed circuit with a classifier, 'in which the .discharge of thegrinding mill is separated g into a finishedproduct, accompanied by aeci relatively large quantity of water, dischar ed by overflowing at oneend of'the classi er, and intoasandy or coarse product, accompanied by arelatively small amount of water, discharged at the opposite end oftheiclassi- :5 fier, the coarse or oversize product being returned tothe mill forfurther reduction in 7 size. If the ore be treated withgaseous acetylene in the conventional installation wherein the mill isnot gas-tight,- such treatment would be too expensive becauseof leakageof the acet lene and hazardous because acetye lenemixe with air ishighly explosive.

It was'suggested that the'wet grinding might be done in batches-in aclosed mill, but while this might be practical for the laboratory,grinding in batches is impracticable in the field because of thecomplications and consequent expense of introducing intermittentoperations into what are.oth'erwise con- 40 tinuous. Any means forreducing the cost and'hazard of using acetylene must be simple,cheap'and adapted'for use with existing methods and apparatus.Experimental work disclosed that the oversize material to be re-.

7 turned to the grindin mill from the classifier would clog or cho e inanyform of pipe or conduitconnecting the two and adapted to maintain themill gas-tight, as for example a U seal. A sump and pump were sug gestedbut the abrasive character of the materials and the small percentage ofwater a1- lowable rendered this apparatus impracticable; If water wereadded to makea freely flowing material capable of bein pumped objectionswould result. xcess wapense in gas required, and additional means forseparating the water from the ore to be ground would be required.Alsouthe grind ing capacity of the mill isgreatly reduced when too muchwater is present, and if the mill is flooded the filming operation willnot be as satisfactory as when gas can more read 1 ily contact with theore, so that a small:

amount of water is desirable, the amount dea pending on the type of oreand other practical considerations, the customary density in thegrinding mill varying from about 50% of water to ore down to about 30%of water to ore. Another diificulty has been in the necessity of feedingthe material at varying rates as supplied from the classifier.

Also withball mills incontinuous operation the device must allow theintroduction of new ballsto replace those worn out, without breaking theseal and allowing air to enter the mill or gas. to escape.

The art remained in this situation for some time, the advantages offilming ,with acetylene were realized but because of the practicaldifliculty of makingthe' operation economical and safe it was suggestedthat the:

application of filming with acetylene to the existing practice in millsbe dropped. Under this invention these .difliculties have been overcomeand a simple, safe, inexpensive means devised which is adaptable toexisting apparatus.

According to this invention, the feedin of wet crushed ore into asubstantially gas-tight enclosure is accomplished by shortening the feedpassage because of the clogging tend-. ency and then making use oftheclogging character of the material to form a substanthe same isadvanced into the enclosure. pe-

cifically the means for doing this is located between discharge end of aclassifier and an enclosing casing around the usual scoop on the feedend of a ball mill and comprises 'somemeans such as a feed screw capableof exerting pressure upon a gas-tight plugof this material formed in ashort passage between the end ofthe screw and the gas-tight enclosure,the mill being made as-tight around'its bearings, etc. and the disc argeof the mill being arranged to take place below the water level in theclassifier; To conserve acetylene, the overflow of the classifier may besubjected to a vacuum or any other separating treatment by which theabsorbed gas or a portion-or all of the accompanying wa ter may be'removed from the ore and returned to the grinding mill for use overofthe device in'Fig. 1;

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be ground, from a'crusher.

Fig- 3 is a right end view partly .in section of the device in Fig. 1;and

Fig. 4 shows a modified construction of the discharge from the screwfeed.

Fig. 5 is a modified construction with the feed screw arranged at anangle.

Fig. 6 is another constructionwith the feed screw vertically disposed.

For purposes of illustration, the invention is shown in connection witha conical ball mill 10 in closed circuit with an inclined typeclassifier 11 as is common. For the sake of clearness, the mechanism formoving the material up the incline in the classifier has not been shown.The feed end of the mill is provided with a gas-tight casing 12 in whichis located a eonventional feed scoop 13. A

feed screw 14 pushes the wet crushed material into the casing 12. abovethe feed screw receives, the coarse material discharged at the upper endof the classifier. Material is supplied to this closed circuitpreferably to the portion'that is not gas-tight, as for example into thehopper 15 from the chute 29, receiving the material to The dischargefrom the mill is through the pipe 16 extending to below water level inthe classifier. As illustrated, a convenient manner of attaching thedischarge pipe .16, is a sheet metal housing 17 secured to onebearingand extended around the discharge from the mill, the pipe 16 being fixedto the 'end of the housing 17 by a gas-tight connection.

The water and fine material overflowing from the classifier maybe passedthrough a pipe 32, a thickener 33 or other separator and the excesswater in whole or in part is preferably returned through a pump 34 andthe pipes 18, 19, 20 and 21 f0r use again in the mill 10 foraddingsufiicient water to the ore at the entrance of passage 25 tosubmerge the A hopper 15 located ore and form the gas-ti ht plug, forc0nveying the crushed ore to t e classifier through the pipe 16, andforadding water for other.

' 19, the hopper 15 and the screw 14 or through the pipe 20 to thehousing 12 because enough water may not enter with .the feed, and againthrough the pipe 21 at the discharge end of the mill to prevent thedischarged material clogging in the pipe 16 and at the same-time furnishthe necessary dilution of the pulp as required for the proper operationof the classifier. A pipe 22 supplies'fresh water at the beginning ofthe operation, and the valves indicated enable this to be cut off andthe water containing absorbed gas to be used Instead of rerunning thewater sep'alater. rated from the finely ground finished product, all ora portion of it may be passed through the vacuum apparatus 23 in a sprayor over the customarv baflies so that the acetylene may be drawn offthrough the pipe 35, compressed and returned through the pipe 24 for usein the mill. The acetylene is preferably supplied from the pipe 24 tothe casing 12, the portion of the circuit between the feed screw 14 andthe end of the discharge pipe 16 being substantially gas-tight. This mayrequire that all bolts and packing be'carefully gone over to make theentiremill and easing substantially gas-tight. Instead of supplyingacetylene in gaseous form, it may be generated within the apparatus by.feeding calcium carbide into the grinding chamber or enclosure as forexample, with crushed ore through the hopper 15, but other suitablegastight supply means may be usedfor introducing the carbide, The use ofcarbide has an advantage over the introduction of gaseous acetylene inthat the calcium hydroxide formed facilitates filming. This hydroxide orsome other alkaline substance may be introduced with the ore to insurefilming in the presence of alkaline material.

The feed screw 14; in the embodiment illustrated. is not provided withany bearing at the end adjacent the casing 12. A short substantiallystraight passage is left between the end of the screw 14 and the casing12. It has been found that the tendency of the wet crushed ore to set orclog in this short straight passage is suflicient to form asubstantially gas-tight plug between the screw 14 and casing 12 withinthe passage 25. In Fig. 4, a modified construction is shown for thepassage 25, in which a tapered constriction 26 is placed in this passagefor the purpose of offering a little more resistance to the movein themill and casing may be partially withdrawn through the pipe 28, or adiluent such as nitrogen may be suppliedto 'reducethe hazard. ofoxygenpresenti- With the feed screw arranged at an angle as in Fig.,5,;it"hasbeen found that a more effective and gas-tight plug is formed with someores. Preferably the plug seal and other details are similar to thosepreviously mentioned; The constriction of Fig. 4 may be gsed with thefeed passages arranged as in igs. 5 and 6. The vertical position for thefeed screw inFig. 6 illustrates another embodiment of this invention,the other details being as described in connection with Fi s. 1;to'3.'

. mong the advantages of this invention may be enumeratedits simplicity,cheapness, and adaptability for use with existing types of apparatus,particularly to grindin mills. The use of the feed screw ermits aditional balls to be'fed in with the material from the hopper to replaceballs within the mill which have worn'out. The use of the rela-'.tive'ly short, substantially straight, passage is effective in combattinthe clogging tendency of the material an yet this tendency is-present toan extent sufiicient to form the material into a substantiall gas-tightplug fitting with saidpassage. other ad vantage of this invention isthat it is adapted to meet the needs of the irre lar rates of feedexperienced in the field or it will be seen from Figs. 3, .5' and 6 ofthe drawings that even though the feed from the screw .14 be greatlyreduced, the plug is still maintained within the passage 25. I

Nothing has been said about the exact size of feed material or preciseamount of water to be supplied because these features have been found tobe widely variable with the different types of ores treated. Of course,if the material from the-crusher is too coarse, it will not be effectivein forming the plu desired in the passage 25, but experience wi soonshow how small the material should be; That crushed to sizes of one-halfinch hasbeen found generally suitable, although larger-sizes may, withsome ores, be permissible, 1

if the coarse material of the classifier suflices to maintain aneffective gas-tight plug.

What is claimed is:

1. The method of feeding crushed wet ore into a' substantially gas-tightenclosure,

.closure, feeding ore same is advanced, supplying water to theenclosure, grinding the carbide and wet ore 'which'comprises formingtheore into a substantially gas-tight plug, pushing the plug into theenclosure, feeding said wet ore behind the plug, and compacting the feedto maintain the plug as the same is advanced.

2. The method of feeding crushed wet copper ore containing oxidizedcopper minerals into a gas-tight enclosure, which comprises compactingthe ore beneath a liquid seal into a substantially gas-tight plug withina short passage, feeding the ore behind the plug, compacting the feedwhile building onto said plug, and pushing the same through said .passae The method of feeding, copper ore concarbonate copper minerals into agas-tig t enclosure, which comprises supplymgwater to the crushed ore,compacting the wet ore into a short gas-tight plug, feeding the wet orebehind said plug, compacting the feed while building'onto said plug, andpushing the plug into said enclosure.

4. The method of filming ore with acetylene which comprises grindingsaid ore in a substantially gas-tight enclosure in the pres 3. taininence of acetylene,- while feeding said ore into said enclosure insuchmanner as to preclude substantial leakage of acetylene from" or ofoxygen into said enclosure.

5. The continuous method of filming oxidized copper ore that comprisesfeeding such ore-into a substantially gas-tight grinding chamber in suchmanner as topreclude substantial leakage of oxygen into said chamberor-gas therefrom; grinding such ore in said chamber in the presence ofacetylene and continuously discharging ground ore from said chamber insuch manner-as to preclude substantial leakage of oxygen into saidchamber 'or of gas therefrom.

6. The method of filming crushed wet ore with acetylene'which comprisesforming the ore into a substantially gas-tight plug, pushing the pluginto a substantially gas-tight enclosure, supplying calcium carbidetothe enbehind said plug as the within said enclosure, and dischargingthe ground filmed ore below the surface of a liquid seal;

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7. The method of filming crushed ore with I acetylene Which-comprisesforming the ore into a substantially gas-tight plug, pushing the plug.into a substantially gas-tight en-.

closure, feeding ore behind the plug, compacting the feed to "maintainthe plug as the same is advanced,- wetting the ore, grinding the wet orewithin said gas-tight enclosure in the presence of acetylene, anddischarging the ground filmed ore below the surface of a liquid seal.-

8. The methodof filming crushed wet ore with acetylene in asubstantially gas-tight grinding mill", which comprises supplying 10.The method of filmingcrushe d wet ore with acetylene in a's ubstantiallygas-tight grinding mill, which comprises supplying water to the mill,separating water from solid particles in the mill discharge, withdrawingabsorbed acetvlenc from at least a portion of the separated water underreduced pressure, compressing the acetylene, and recycling the samethrough themill.

11. The combination with a substantially gas-tight enclosure, of meansfor feeding crushed oreinto said enclosure, which comprises a shortsubstantially straight passage leading into the enclosure, means forwetting the ore before entering said passage, means for compacting thewet ore to form a substantially gas-tightplug within said passage, meansfor pushing the plug through the passage into the enclosure, means forfeeding ores behind said plug, and means for compacting the feed tobuild onto and maintain the plug as the material is moved through saidpassage. v

12. The combination With-a substantially gas-tight grinding mill, ofmeans for feed ing crushed ore into said m'ill'while maintain ing themill gas-tight, means for supplying water to said mill, means formaintaining acetylene within the mill, discharge means for the mill, anda liquid seal on the discharge means from said mill.

13. The combination with a classifier, of means to enclose saidclassifier so as to prevent the escape of gases therefrom; asubstantially gas-tight grinding mill'in closed cir cuit, with saidclassifier, means for feeding material to said circuit, a substantiallygastight enclosure at the feed end of-said mill,

means for raising material within said 0l1' closure, feeding the same tosaid mill, and

' means for feeding thecoarse material discharged from said classifier;into said e11- closure 14. The combination with a classifier. of meansto enclose said'cl'assifier so as to prevent the escape oftherefrom,'assuhstantially gas-tight grinding mill in closed circuitwith said classifier, 1neans for feeding crushed wct'ore into said mill.means for maintaimng acetylene 1n said mil], means for supplying waterto the mill, means for dis-- charging the material from said mill belowthe water level in said classifier, and means for. recycling at least aportion of the water containing absorbed acetylene, through the mill.

15, The combination with a substantially gas-tight enclosure, of a screwfor feedingmaterial thereinto, a short substantially straight passagebetween said screw and enclosure, and having a tapered constrictiontherein for compacting the material.

' 17. The combination with a substantially gas-tight enclosure, of ascrew for feeding "material thereinto, a. short substantially straightpassage between said screw and enclosure, and an agitator to break upthe material at the discharge end of said passage.

18. An ore filming device which comprises agas-tightenclosure whichincludes a mill capable of grinding ore in the presence of afilm-producing gas, a passage to introduce ore into said enclosure,means in said passage to form a seal at the feed-end of said enclosure,gas-tight means to separate ore discharged from said mill, and agas-tight connection on said mill and separator for discharging thecontents of said mill and for conducting the same to the separator.

19. An ore filming device comprising a gastight enclosure for grindingore in the presence of a film-producing gas, feeding means to introduceore into said enclosure, means to form a seal in said feeding means, agas tight means to separate coarse aggregates of ore and to return thesame to the feeding means, and means to separate gas-charged water fromthe ground ore and to return at least a part of said water to thefeeding means.

520. The combination with a classifier having meansto discharge finelyground ore and means to discharge coarse aggregates of ore, of means toenclose said classifier so as to retain gases therein, a feed pipe forsaid classitier, an air-tight enclosure including a grinding mill and achamber, the discharge of said mill being connected-with the feed pipeof said classifier, scoop means in said chamber to feed ore to saidmill, and means between the discharge for coarse aggregates and thechamber to form a plug of ore and continuously advance the same into thechamber.

In 'testimony whereof, I allix my signaturc.

' 1 JOHN M. CALLOVV.

